The object of this proposal is to synthesize a series of polycyclic organic molecules bearing nitrogen binding sites for metal ions and to test their ion selectivity. The target systems were chosen for their rigidity and expected size-selectivity in forming inclusion complexes which will be soluble in organic solvents. Potential applications include ion-selective electrodes, membrane metal separation and modeling of biomembrane ion channels. The proposed syntheses of large ring (18 to 24-membered) macrocycles involve oxidation of ketone enolates to provide oligomeric 1,4-diketones, which may be converted to furans or pyrroles. Target macrocycles containing pyridine binding sites are to be synthesized by condensing appropriate aromatic amines with ketoesters, followed by aromatization of the resulting pyridone rings. Six and seven-dentate helical ligands are also proposed, as well as helical polymers which may form ion conducting channels in membranes.